Food intake control is practiced in the commercial production of poultry and other animals under various circumstances. In particular, reducing the food intake of chickens is very important. For example, in the rearing of broiler breeder replacement pullets and roosters, it is essential that food intake be controlled in order to prevent obesity which would result in reduced reproductive performance.
Currently, a common method of accomplishing food intake control in broiler breeder chickens is through a "skip-a-day" program in which the birds are fasted every other day. Also, at the end of the first laying cycle, commercial laying hens are commonly forced molted by removal of food and water for a period of time. Force molting causes laying hens to enter a second egg-laying cycle, thereby increasing the egg output of the birds. Although such fasting procedures are effective for both the rearing of broiler breeders and for forced molting of commercial laying hens, animal welfare groups have complained that these fasting procedures for controlling food intake in poultry are inhumane.
In addition, interest has recently developed in the possible physical restriction of feed intake in broilers during the early stages of life followed by ad libitum feeding. This procedure has been reported as resulting compensatory growth and increased efficiency of meat production. However, physical restriction of feed under commercial broiler production conditions would be difficult to manage and accomplish since such restriction often requires substantial labor or mechanization.
In the area of egg productivity of chickens, Japanese Patent 52-50881 discloses that lower fatty acids, such as formic, acetic, propionic and butyric acids, increase a chicken's egg productivity and reduce a chicken's feed intake ratio. Feed intake ratio is defined as the ratio of weight of feed intake to unit weight of eggs. However, the Japanese patent does not specifically disclose that the actual amount of feed intake is reduced, but only that the ratio of feed intake per egg productivity is reduced.
Nevertheless, control of food intake in chickens has been effected by the dietary addition of certain organic chemicals. For example, a 3% supplementary level of the amino acid glycine is known to reduce food intake of broiler chicks 1-21 days of age by approximately 17%-20%. Cave, Effect of Dietary Glycine on Feed Intake and Growth of Meat- and Egg-Strain Chicks", Poultry Sci., 57: 1605-1608 (1978); Cave, "Glycine- and Fatty-Acid Induced Restriction of Food Intake", Poultry Sci., 62: 125-132 (1982). However, food intake reduction greater than 17%-20% is desirable. Moreover, excessive dietary glycine is known to be ineffective in reducing food intake of chicks beyond 28 days of age. Ibid.
In addition, in diets containing 3% corn oil, complete replacement of the corn oil with propionic, caprylic, capric or lauric acids for corn oil reduced food intake of broiler chickens at 7-21 days of age, but at a maximum food intake reduction of only 11%. Cave, "Effect of Dietary Short- and Medium-Chain Fatty Acids on Feed Intake by Chicks", Poultry Sci., 61: 1147-1153 (1982). At the highest level of dietary supplementation (10%), caprylic acid reduced 9-29 day food intake by about 37% while lauric acid decreased food intake by 48%. Ibid. Dietary lauric acid supplementation (20% of the diet) caused complete feed refusal in some laying hens and had an irritating effect on at least part of the gastro-intestinal tract in young chicks. Renner et al., "Utilization of Fatty Acids by The Chicken", J. Nutr., 74: 259-264 (1961).
Further, 0-42 days of age broiler chicks fed a diet supplemented with ammonium sulphate at 1.38% showed reduced food intake by about 7%. Cave, "Use of Dietary Ammonium Sulphate in Control of Growth Rate of Broiler Breeder Replacement Pullets From One Day of Age", Poultry Sci., 61: 1859-1865 (1982). Moreover, a dietary level of 2.75% ammonium sulphate reduced broiler chick food intake at the 0-28 and 42 day age periods by approximately 27% and 22% respectively. Ibid.
Therefore, the methods of dietary addition used in the past are unsatisfactory because the amount of food intake reduction is not sufficient at dietary levels of 3% or less. In addition, at higher levels of dietary addition, there are, in some cases, complete feed refusal or irritation and deleterious physical effects.
It can thus be readily appreciated that provision of a method for controlling food intake in poultry, particularly chickens, which method provides a high level of food intake reduction in poultry with a low level of dietary addition, and eliminates the previously discussed problems, would be a highly desirable advance over the current state of the art in food intake control.